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Unified Diff: webrtc/modules/audio_processing/level_controller/signal_classifier.cc

Issue 2090583002: New module for the adaptive level controlling functionality in the audio processing module (Closed) Base URL: https://chromium.googlesource.com/external/webrtc.git@master
Patch Set: Corrected an assignment error Created 4 years, 6 months ago
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Index: webrtc/modules/audio_processing/level_controller/signal_classifier.cc
diff --git a/webrtc/modules/audio_processing/level_controller/signal_classifier.cc b/webrtc/modules/audio_processing/level_controller/signal_classifier.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b338ad3ff2378f0a8eaea1a4d5fa5622eff915fe
--- /dev/null
+++ b/webrtc/modules/audio_processing/level_controller/signal_classifier.cc
@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ * Use of this source code is governed by a BSD-style license
+ * that can be found in the LICENSE file in the root of the source
+ * tree. An additional intellectual property rights grant can be found
+ * in the file PATENTS. All contributing project authors may
+ * be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/modules/audio_processing/level_controller/signal_classifier.h"
+
+#include <algorithm>
+#include <numeric>
+#include <vector>
+
+#include "webrtc/base/array_view.h"
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/audio_processing/aec/aec_rdft.h"
+#include "webrtc/modules/audio_processing/audio_buffer.h"
+#include "webrtc/modules/audio_processing/level_controller/down_sampler.h"
+#include "webrtc/modules/audio_processing/level_controller/noise_spectrum_estimator.h"
+#include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
+
+namespace webrtc {
+namespace {
+
+void RemoveDcLevel(rtc::ArrayView<float> x) {
+ RTC_DCHECK_LT(0u, x.size());
+ float mean = std::accumulate(x.data(), x.data() + x.size(), 0.f);
+ mean /= x.size();
+
+ for (float& v : x) {
+ v -= mean;
+ }
+}
+
+void PowerSpectrum(rtc::ArrayView<const float> x,
+ rtc::ArrayView<float> spectrum) {
+ RTC_DCHECK_EQ(65u, spectrum.size());
+ RTC_DCHECK_EQ(128u, x.size());
+ float X[128];
+ std::copy(x.data(), x.data() + x.size(), X);
+ aec_rdft_forward_128(X);
+
+ float* X_p = X;
+ RTC_DCHECK_EQ(X_p, &X[0]);
+ spectrum[0] = (*X_p) * (*X_p);
+ ++X_p;
+ RTC_DCHECK_EQ(X_p, &X[1]);
+ spectrum[64] = (*X_p) * (*X_p);
+ for (int k = 1; k < 64; ++k) {
+ ++X_p;
+ RTC_DCHECK_EQ(X_p, &X[2 * k]);
+ spectrum[k] = (*X_p) * (*X_p);
+ ++X_p;
+ RTC_DCHECK_EQ(X_p, &X[2 * k + 1]);
+ spectrum[k] += (*X_p) * (*X_p);
+ }
+}
+
+webrtc::SignalClassifier::SignalType ClassifySignal(
+ rtc::ArrayView<const float> signal_spectrum,
+ rtc::ArrayView<const float> noise_spectrum,
+ ApmDataDumper* data_dumper) {
+ int num_stationary_bands = 0;
+ int num_highly_nonstationary_bands = 0;
+
+ // Detect stationary and highly nonstationary bands.
+ for (size_t k = 1; k < 40; k++) {
+ if (signal_spectrum[k] < 3 * noise_spectrum[k] &&
+ signal_spectrum[k] * 3 > noise_spectrum[k]) {
+ ++num_stationary_bands;
+ } else if (signal_spectrum[k] > 9 * noise_spectrum[k]) {
+ ++num_highly_nonstationary_bands;
+ }
+ }
+
+ data_dumper->DumpRaw("lc_num_stationary_bands", 1, &num_stationary_bands);
+ data_dumper->DumpRaw("lc_num_highly_nonstationary_bands", 1,
+ &num_highly_nonstationary_bands);
+
+ // Use the detected number of bands to classify the overall signal
+ // stationarity.
+ if (num_stationary_bands > 15) {
+ return SignalClassifier::SignalType::kStationary;
+ } else if (num_highly_nonstationary_bands > 15) {
+ return SignalClassifier::SignalType::kHighlyNonStationary;
+ } else {
+ return SignalClassifier::SignalType::kNonStationary;
+ }
+}
+
+} // namespace
+
+class FrameExtender {
+ public:
+ FrameExtender(size_t frame_size, size_t extended_frame_size)
+ : x_old_(extended_frame_size - frame_size, 0.f) {}
+
+ void ExtendFrame(rtc::ArrayView<const float> x,
+ rtc::ArrayView<float> x_extended) {
+ RTC_DCHECK_EQ(x_old_.size() + x.size(), x_extended.size());
+ std::copy(x_old_.data(), x_old_.data() + x_old_.size(), x_extended.data());
+ std::copy(x.data(), x.data() + x.size(), x_extended.data() + x_old_.size());
+ std::copy(x_extended.data() + x_extended.size() - x_old_.size(),
+ x_extended.data() + x_extended.size(), x_old_.data());
+ }
+
+ private:
+ std::vector<float> x_old_;
+
+ RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(FrameExtender);
+};
+
+SignalClassifier::SignalClassifier(ApmDataDumper* data_dumper)
+ : data_dumper_(data_dumper),
+ down_sampler_(data_dumper_),
+ noise_spectrum_estimator_(data_dumper_) {
+ Initialize(AudioProcessing::kSampleRate48kHz);
+}
+SignalClassifier::~SignalClassifier() {}
+
+void SignalClassifier::Initialize(int sample_rate_hz) {
+ aec_rdft_init();
+ down_sampler_.Initialize(sample_rate_hz);
+ frame_extender_.reset(new FrameExtender(80, 128));
+ sample_rate_hz_ = sample_rate_hz;
+ initialization_frames_left_ = 2;
+ consistent_classification_counter_ = 3;
+ last_signal_type_ = SignalClassifier::SignalType::kNonStationary;
+}
+
+void SignalClassifier::Analyze(const AudioBuffer& audio,
+ SignalType* signal_type) {
+ // Compute the signal power spectrum.
+ float downsampled_frame[80];
+ down_sampler_.DownSample(rtc::ArrayView<const float>(
+ audio.channels_const_f()[0], audio.num_frames()),
+ downsampled_frame);
+ float extended_frame[128];
+ frame_extender_->ExtendFrame(downsampled_frame, extended_frame);
+ RemoveDcLevel(extended_frame);
+ float signal_spectrum[65];
+ PowerSpectrum(extended_frame, signal_spectrum);
+
+ // Classify the signal based on the estimate of the noise spectrum and the
+ // signal spectrum estimate.
+ *signal_type = ClassifySignal(signal_spectrum,
+ noise_spectrum_estimator_.GetNoiseSpectrum(),
+ data_dumper_);
+
+ // Update the noise spectrum based on the signal spectrum.
+ noise_spectrum_estimator_.Update(signal_spectrum,
+ initialization_frames_left_ > 0);
+
+ // Update the number of frames until a reliable signal spectrum is achieved.
+ initialization_frames_left_ = std::max(0, initialization_frames_left_ - 1);
+
+ if (last_signal_type_ == *signal_type) {
+ consistent_classification_counter_ =
+ std::max(0, consistent_classification_counter_ - 1);
+ } else {
+ last_signal_type_ = *signal_type;
+ consistent_classification_counter_ = 3;
+ }
+
+ if (consistent_classification_counter_ > 0) {
+ *signal_type = SignalClassifier::SignalType::kNonStationary;
+ }
+}
+
+} // namespace webrtc

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